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From: Erez Zadok <ezk@cs.sunysb.edu>
To: hch@infradead.org, viro@ftp.linux.org.uk, akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
       Erez Zadok <ezk@cs.sunysb.edu>
Subject: [PATCH 12/42] Unionfs: common file copyup/revalidation operations
Date: Sun,  9 Dec 2007 21:41:45 -0500
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Includes open, ioctl, and flush operations.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
---
 fs/unionfs/commonfops.c |  827 +++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 827 insertions(+), 0 deletions(-)
 create mode 100644 fs/unionfs/commonfops.c

diff --git a/fs/unionfs/commonfops.c b/fs/unionfs/commonfops.c
new file mode 100644
index 0000000..f714e2f
--- /dev/null
+++ b/fs/unionfs/commonfops.c
@@ -0,0 +1,827 @@
+/*
+ * Copyright (c) 2003-2007 Erez Zadok
+ * Copyright (c) 2003-2006 Charles P. Wright
+ * Copyright (c) 2005-2007 Josef 'Jeff' Sipek
+ * Copyright (c) 2005-2006 Junjiro Okajima
+ * Copyright (c) 2005      Arun M. Krishnakumar
+ * Copyright (c) 2004-2006 David P. Quigley
+ * Copyright (c) 2003-2004 Mohammad Nayyer Zubair
+ * Copyright (c) 2003      Puja Gupta
+ * Copyright (c) 2003      Harikesavan Krishnan
+ * Copyright (c) 2003-2007 Stony Brook University
+ * Copyright (c) 2003-2007 The Research Foundation of SUNY
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include "union.h"
+
+/*
+ * 1) Copyup the file
+ * 2) Rename the file to '.unionfs<original inode#><counter>' - obviously
+ * stolen from NFS's silly rename
+ */
+static int copyup_deleted_file(struct file *file, struct dentry *dentry,
+			       int bstart, int bindex)
+{
+	static unsigned int counter;
+	const int i_inosize = sizeof(dentry->d_inode->i_ino) * 2;
+	const int countersize = sizeof(counter) * 2;
+	const int nlen = sizeof(".unionfs") + i_inosize + countersize - 1;
+	char name[nlen + 1];
+	int err;
+	struct dentry *tmp_dentry = NULL;
+	struct dentry *lower_dentry;
+	struct dentry *lower_dir_dentry = NULL;
+
+	lower_dentry = unionfs_lower_dentry_idx(dentry, bstart);
+
+	sprintf(name, ".unionfs%*.*lx",
+		i_inosize, i_inosize, lower_dentry->d_inode->i_ino);
+
+	/*
+	 * Loop, looking for an unused temp name to copyup to.
+	 *
+	 * It's somewhat silly that we look for a free temp tmp name in the
+	 * source branch (bstart) instead of the dest branch (bindex), where
+	 * the final name will be created.  We _will_ catch it if somehow
+	 * the name exists in the dest branch, but it'd be nice to catch it
+	 * sooner than later.
+	 */
+retry:
+	tmp_dentry = NULL;
+	do {
+		char *suffix = name + nlen - countersize;
+
+		dput(tmp_dentry);
+		counter++;
+		sprintf(suffix, "%*.*x", countersize, countersize, counter);
+
+		pr_debug("unionfs: trying to rename %s to %s\n",
+			 dentry->d_name.name, name);
+
+		tmp_dentry = lookup_one_len(name, lower_dentry->d_parent,
+					    nlen);
+		if (IS_ERR(tmp_dentry)) {
+			err = PTR_ERR(tmp_dentry);
+			goto out;
+		}
+	} while (tmp_dentry->d_inode != NULL);	/* need negative dentry */
+	dput(tmp_dentry);
+
+	err = copyup_named_file(dentry->d_parent->d_inode, file, name, bstart,
+				bindex,
+				i_size_read(file->f_path.dentry->d_inode));
+	if (err) {
+		if (unlikely(err == -EEXIST))
+			goto retry;
+		goto out;
+	}
+
+	/* bring it to the same state as an unlinked file */
+	lower_dentry = unionfs_lower_dentry_idx(dentry, dbstart(dentry));
+	if (!unionfs_lower_inode_idx(dentry->d_inode, bindex)) {
+		atomic_inc(&lower_dentry->d_inode->i_count);
+		unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+					    lower_dentry->d_inode);
+	}
+	lower_dir_dentry = lock_parent(lower_dentry);
+	err = vfs_unlink(lower_dir_dentry->d_inode, lower_dentry);
+	unlock_dir(lower_dir_dentry);
+
+out:
+	if (!err)
+		unionfs_check_dentry(dentry);
+	return err;
+}
+
+/*
+ * put all references held by upper struct file and free lower file pointer
+ * array
+ */
+static void cleanup_file(struct file *file)
+{
+	int bindex, bstart, bend;
+	struct file **lower_files;
+	struct file *lower_file;
+	struct super_block *sb = file->f_path.dentry->d_sb;
+
+	lower_files = UNIONFS_F(file)->lower_files;
+	bstart = fbstart(file);
+	bend = fbend(file);
+
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		int i;	/* holds (possibly) updated branch index */
+		int old_bid;
+
+		lower_file = unionfs_lower_file_idx(file, bindex);
+		if (!lower_file)
+			continue;
+
+		/*
+		 * Find new index of matching branch with an open
+		 * file, since branches could have been added or
+		 * deleted causing the one with open files to shift.
+		 */
+		old_bid = UNIONFS_F(file)->saved_branch_ids[bindex];
+		i = branch_id_to_idx(sb, old_bid);
+		if (unlikely(i < 0)) {
+			printk(KERN_ERR "unionfs: no superblock for "
+			       "file %p\n", file);
+			continue;
+		}
+
+		/* decrement count of open files */
+		branchput(sb, i);
+		/*
+		 * fput will perform an mntput for us on the correct branch.
+		 * Although we're using the file's old branch configuration,
+		 * bindex, which is the old index, correctly points to the
+		 * right branch in the file's branch list.  In other words,
+		 * we're going to mntput the correct branch even if branches
+		 * have been added/removed.
+		 */
+		fput(lower_file);
+		UNIONFS_F(file)->lower_files[bindex] = NULL;
+		UNIONFS_F(file)->saved_branch_ids[bindex] = -1;
+	}
+
+	UNIONFS_F(file)->lower_files = NULL;
+	kfree(lower_files);
+	kfree(UNIONFS_F(file)->saved_branch_ids);
+	/* set to NULL because caller needs to know if to kfree on error */
+	UNIONFS_F(file)->saved_branch_ids = NULL;
+}
+
+/* open all lower files for a given file */
+static int open_all_files(struct file *file)
+{
+	int bindex, bstart, bend, err = 0;
+	struct file *lower_file;
+	struct dentry *lower_dentry;
+	struct dentry *dentry = file->f_path.dentry;
+	struct super_block *sb = dentry->d_sb;
+
+	bstart = dbstart(dentry);
+	bend = dbend(dentry);
+
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+		if (!lower_dentry)
+			continue;
+
+		dget(lower_dentry);
+		unionfs_mntget(dentry, bindex);
+		branchget(sb, bindex);
+
+		lower_file =
+			dentry_open(lower_dentry,
+				    unionfs_lower_mnt_idx(dentry, bindex),
+				    file->f_flags);
+		if (IS_ERR(lower_file)) {
+			err = PTR_ERR(lower_file);
+			goto out;
+		} else {
+			unionfs_set_lower_file_idx(file, bindex, lower_file);
+		}
+	}
+out:
+	return err;
+}
+
+/* open the highest priority file for a given upper file */
+static int open_highest_file(struct file *file, bool willwrite)
+{
+	int bindex, bstart, bend, err = 0;
+	struct file *lower_file;
+	struct dentry *lower_dentry;
+	struct dentry *dentry = file->f_path.dentry;
+	struct inode *parent_inode = dentry->d_parent->d_inode;
+	struct super_block *sb = dentry->d_sb;
+
+	bstart = dbstart(dentry);
+	bend = dbend(dentry);
+
+	lower_dentry = unionfs_lower_dentry(dentry);
+	if (willwrite && IS_WRITE_FLAG(file->f_flags) && is_robranch(dentry)) {
+		for (bindex = bstart - 1; bindex >= 0; bindex--) {
+			err = copyup_file(parent_inode, file, bstart, bindex,
+					  i_size_read(dentry->d_inode));
+			if (!err)
+				break;
+		}
+		atomic_set(&UNIONFS_F(file)->generation,
+			   atomic_read(&UNIONFS_I(dentry->d_inode)->
+				       generation));
+		goto out;
+	}
+
+	dget(lower_dentry);
+	unionfs_mntget(dentry, bstart);
+	lower_file = dentry_open(lower_dentry,
+				 unionfs_lower_mnt_idx(dentry, bstart),
+				 file->f_flags);
+	if (IS_ERR(lower_file)) {
+		err = PTR_ERR(lower_file);
+		goto out;
+	}
+	branchget(sb, bstart);
+	unionfs_set_lower_file(file, lower_file);
+	/* Fix up the position. */
+	lower_file->f_pos = file->f_pos;
+
+	memcpy(&lower_file->f_ra, &file->f_ra, sizeof(struct file_ra_state));
+out:
+	return err;
+}
+
+/* perform a delayed copyup of a read-write file on a read-only branch */
+static int do_delayed_copyup(struct file *file)
+{
+	int bindex, bstart, bend, err = 0;
+	struct dentry *dentry = file->f_path.dentry;
+	struct inode *parent_inode = dentry->d_parent->d_inode;
+
+	bstart = fbstart(file);
+	bend = fbend(file);
+
+	BUG_ON(!S_ISREG(dentry->d_inode->i_mode));
+
+	unionfs_check_file(file);
+	unionfs_check_dentry(dentry);
+	for (bindex = bstart - 1; bindex >= 0; bindex--) {
+		if (!d_deleted(dentry))
+			err = copyup_file(parent_inode, file, bstart,
+					  bindex,
+					  i_size_read(dentry->d_inode));
+		else
+			err = copyup_deleted_file(file, dentry, bstart,
+						  bindex);
+
+		if (!err)
+			break;
+	}
+	if (err || (bstart <= fbstart(file)))
+		goto out;
+	bend = fbend(file);
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		if (unionfs_lower_file_idx(file, bindex)) {
+			branchput(dentry->d_sb, bindex);
+			fput(unionfs_lower_file_idx(file, bindex));
+			unionfs_set_lower_file_idx(file, bindex, NULL);
+		}
+		if (unionfs_lower_mnt_idx(dentry, bindex)) {
+			unionfs_mntput(dentry, bindex);
+			unionfs_set_lower_mnt_idx(dentry, bindex, NULL);
+		}
+		if (unionfs_lower_dentry_idx(dentry, bindex)) {
+			BUG_ON(!dentry->d_inode);
+			iput(unionfs_lower_inode_idx(dentry->d_inode, bindex));
+			unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+						    NULL);
+			dput(unionfs_lower_dentry_idx(dentry, bindex));
+			unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+		}
+	}
+	/* for reg file, we only open it "once" */
+	fbend(file) = fbstart(file);
+	set_dbend(dentry, dbstart(dentry));
+	ibend(dentry->d_inode) = ibstart(dentry->d_inode);
+
+out:
+	unionfs_check_file(file);
+	unionfs_check_dentry(dentry);
+	return err;
+}
+
+/*
+ * Revalidate the struct file
+ * @file: file to revalidate
+ * @willwrite: true if caller may cause changes to the file; false otherwise.
+ */
+int unionfs_file_revalidate(struct file *file, bool willwrite)
+{
+	struct super_block *sb;
+	struct dentry *dentry;
+	int sbgen, fgen, dgen;
+	int bstart, bend;
+	int size;
+	int err = 0;
+
+	dentry = file->f_path.dentry;
+	unionfs_lock_dentry(dentry);
+	sb = dentry->d_sb;
+
+	/*
+	 * First revalidate the dentry inside struct file,
+	 * but not unhashed dentries.
+	 */
+	if (unlikely(!d_deleted(dentry) &&
+		     !__unionfs_d_revalidate_chain(dentry, NULL, willwrite))) {
+		err = -ESTALE;
+		goto out_nofree;
+	}
+
+	sbgen = atomic_read(&UNIONFS_SB(sb)->generation);
+	dgen = atomic_read(&UNIONFS_D(dentry)->generation);
+	fgen = atomic_read(&UNIONFS_F(file)->generation);
+
+	BUG_ON(sbgen > dgen);
+
+	/*
+	 * There are two cases we are interested in.  The first is if the
+	 * generation is lower than the super-block.  The second is if
+	 * someone has copied up this file from underneath us, we also need
+	 * to refresh things.
+	 */
+	if (unlikely(!d_deleted(dentry) &&
+		     (sbgen > fgen || dbstart(dentry) != fbstart(file)))) {
+		/* save orig branch ID */
+		int orig_brid =
+			UNIONFS_F(file)->saved_branch_ids[fbstart(file)];
+
+		/* First we throw out the existing files. */
+		cleanup_file(file);
+
+		/* Now we reopen the file(s) as in unionfs_open. */
+		bstart = fbstart(file) = dbstart(dentry);
+		bend = fbend(file) = dbend(dentry);
+
+		size = sizeof(struct file *) * sbmax(sb);
+		UNIONFS_F(file)->lower_files = kzalloc(size, GFP_KERNEL);
+		if (unlikely(!UNIONFS_F(file)->lower_files)) {
+			err = -ENOMEM;
+			goto out;
+		}
+		size = sizeof(int) * sbmax(sb);
+		UNIONFS_F(file)->saved_branch_ids = kzalloc(size, GFP_KERNEL);
+		if (unlikely(!UNIONFS_F(file)->saved_branch_ids)) {
+			err = -ENOMEM;
+			goto out;
+		}
+
+		if (S_ISDIR(dentry->d_inode->i_mode)) {
+			/* We need to open all the files. */
+			err = open_all_files(file);
+			if (err)
+				goto out;
+		} else {
+			int new_brid;
+			/* We only open the highest priority branch. */
+			err = open_highest_file(file, willwrite);
+			if (err)
+				goto out;
+			new_brid = UNIONFS_F(file)->
+			  saved_branch_ids[fbstart(file)];
+			if (unlikely(new_brid != orig_brid && sbgen > fgen)) {
+				/*
+				 * If we re-opened the file on a different
+				 * branch than the original one, and this
+				 * was due to a new branch inserted, then
+				 * update the mnt counts of the old and new
+				 * branches accordingly.
+				 */
+				unionfs_mntget(dentry, bstart);
+				unionfs_mntput(sb->s_root,
+					       branch_id_to_idx(sb, orig_brid));
+			}
+		}
+		atomic_set(&UNIONFS_F(file)->generation,
+			   atomic_read(
+				   &UNIONFS_I(dentry->d_inode)->generation));
+	}
+
+	/* Copyup on the first write to a file on a readonly branch. */
+	if (willwrite && IS_WRITE_FLAG(file->f_flags) &&
+	    !IS_WRITE_FLAG(unionfs_lower_file(file)->f_flags) &&
+	    is_robranch(dentry)) {
+		pr_debug("unionfs: do delay copyup of \"%s\"\n",
+			 dentry->d_name.name);
+		err = do_delayed_copyup(file);
+	}
+
+out:
+	if (err) {
+		kfree(UNIONFS_F(file)->lower_files);
+		kfree(UNIONFS_F(file)->saved_branch_ids);
+	}
+out_nofree:
+	if (!err)
+		unionfs_check_file(file);
+	unionfs_unlock_dentry(dentry);
+	return err;
+}
+
+/* unionfs_open helper function: open a directory */
+static int __open_dir(struct inode *inode, struct file *file)
+{
+	struct dentry *lower_dentry;
+	struct file *lower_file;
+	int bindex, bstart, bend;
+	struct vfsmount *mnt;
+
+	bstart = fbstart(file) = dbstart(file->f_path.dentry);
+	bend = fbend(file) = dbend(file->f_path.dentry);
+
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		lower_dentry =
+			unionfs_lower_dentry_idx(file->f_path.dentry, bindex);
+		if (!lower_dentry)
+			continue;
+
+		dget(lower_dentry);
+		unionfs_mntget(file->f_path.dentry, bindex);
+		mnt = unionfs_lower_mnt_idx(file->f_path.dentry, bindex);
+		lower_file = dentry_open(lower_dentry, mnt, file->f_flags);
+		if (IS_ERR(lower_file))
+			return PTR_ERR(lower_file);
+
+		unionfs_set_lower_file_idx(file, bindex, lower_file);
+
+		/*
+		 * The branchget goes after the open, because otherwise
+		 * we would miss the reference on release.
+		 */
+		branchget(inode->i_sb, bindex);
+	}
+
+	return 0;
+}
+
+/* unionfs_open helper function: open a file */
+static int __open_file(struct inode *inode, struct file *file)
+{
+	struct dentry *lower_dentry;
+	struct file *lower_file;
+	int lower_flags;
+	int bindex, bstart, bend;
+
+	lower_dentry = unionfs_lower_dentry(file->f_path.dentry);
+	lower_flags = file->f_flags;
+
+	bstart = fbstart(file) = dbstart(file->f_path.dentry);
+	bend = fbend(file) = dbend(file->f_path.dentry);
+
+	/*
+	 * check for the permission for lower file.  If the error is
+	 * COPYUP_ERR, copyup the file.
+	 */
+	if (lower_dentry->d_inode && is_robranch(file->f_path.dentry)) {
+		/*
+		 * if the open will change the file, copy it up otherwise
+		 * defer it.
+		 */
+		if (lower_flags & O_TRUNC) {
+			int size = 0;
+			int err = -EROFS;
+
+			/* copyup the file */
+			for (bindex = bstart - 1; bindex >= 0; bindex--) {
+				err = copyup_file(
+					file->f_path.dentry->d_parent->d_inode,
+					file, bstart, bindex, size);
+				if (!err)
+					break;
+			}
+			return err;
+		} else {
+			lower_flags &= ~(OPEN_WRITE_FLAGS);
+		}
+	}
+
+	dget(lower_dentry);
+
+	/*
+	 * dentry_open will decrement mnt refcnt if err.
+	 * otherwise fput() will do an mntput() for us upon file close.
+	 */
+	unionfs_mntget(file->f_path.dentry, bstart);
+	lower_file =
+		dentry_open(lower_dentry,
+			    unionfs_lower_mnt_idx(file->f_path.dentry, bstart),
+			    lower_flags);
+	if (IS_ERR(lower_file))
+		return PTR_ERR(lower_file);
+
+	unionfs_set_lower_file(file, lower_file);
+	branchget(inode->i_sb, bstart);
+
+	return 0;
+}
+
+int unionfs_open(struct inode *inode, struct file *file)
+{
+	int err = 0;
+	struct file *lower_file = NULL;
+	struct dentry *dentry = NULL;
+	int bindex = 0, bstart = 0, bend = 0;
+	int size;
+
+	unionfs_read_lock(inode->i_sb);
+
+	file->private_data =
+		kzalloc(sizeof(struct unionfs_file_info), GFP_KERNEL);
+	if (unlikely(!UNIONFS_F(file))) {
+		err = -ENOMEM;
+		goto out_nofree;
+	}
+	fbstart(file) = -1;
+	fbend(file) = -1;
+	atomic_set(&UNIONFS_F(file)->generation,
+		   atomic_read(&UNIONFS_I(inode)->generation));
+
+	size = sizeof(struct file *) * sbmax(inode->i_sb);
+	UNIONFS_F(file)->lower_files = kzalloc(size, GFP_KERNEL);
+	if (unlikely(!UNIONFS_F(file)->lower_files)) {
+		err = -ENOMEM;
+		goto out;
+	}
+	size = sizeof(int) * sbmax(inode->i_sb);
+	UNIONFS_F(file)->saved_branch_ids = kzalloc(size, GFP_KERNEL);
+	if (unlikely(!UNIONFS_F(file)->saved_branch_ids)) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	dentry = file->f_path.dentry;
+	unionfs_lock_dentry(dentry);
+
+	bstart = fbstart(file) = dbstart(dentry);
+	bend = fbend(file) = dbend(dentry);
+
+	/*
+	 * open all directories and make the unionfs file struct point to
+	 * these lower file structs
+	 */
+	if (S_ISDIR(inode->i_mode))
+		err = __open_dir(inode, file);	/* open a dir */
+	else
+		err = __open_file(inode, file);	/* open a file */
+
+	/* freeing the allocated resources, and fput the opened files */
+	if (err) {
+		for (bindex = bstart; bindex <= bend; bindex++) {
+			lower_file = unionfs_lower_file_idx(file, bindex);
+			if (!lower_file)
+				continue;
+
+			branchput(file->f_path.dentry->d_sb, bindex);
+			/* fput calls dput for lower_dentry */
+			fput(lower_file);
+		}
+	}
+
+	/* XXX: should this unlock be moved to the function bottom? */
+	unionfs_unlock_dentry(dentry);
+
+out:
+	if (err) {
+		kfree(UNIONFS_F(file)->lower_files);
+		kfree(UNIONFS_F(file)->saved_branch_ids);
+		kfree(UNIONFS_F(file));
+	}
+out_nofree:
+	unionfs_check_inode(inode);
+	if (!err) {
+		unionfs_check_file(file);
+		unionfs_check_dentry(file->f_path.dentry->d_parent);
+	}
+	unionfs_read_unlock(inode->i_sb);
+	return err;
+}
+
+/*
+ * release all lower object references & free the file info structure
+ *
+ * No need to grab sb info's rwsem.
+ */
+int unionfs_file_release(struct inode *inode, struct file *file)
+{
+	struct file *lower_file = NULL;
+	struct unionfs_file_info *fileinfo;
+	struct unionfs_inode_info *inodeinfo;
+	struct super_block *sb = inode->i_sb;
+	struct dentry *dentry = file->f_path.dentry;
+	int bindex, bstart, bend;
+	int fgen, err = 0;
+
+	unionfs_read_lock(sb);
+	/*
+	 * Yes, we have to revalidate this file even if it's being released.
+	 * This is important for open-but-unlinked files, as well as mmap
+	 * support.
+	 */
+	err = unionfs_file_revalidate(file, true);
+	if (unlikely(err))
+		goto out;
+	unionfs_check_file(file);
+	fileinfo = UNIONFS_F(file);
+	BUG_ON(file->f_path.dentry->d_inode != inode);
+	inodeinfo = UNIONFS_I(inode);
+
+	/* fput all the lower files */
+	fgen = atomic_read(&fileinfo->generation);
+	bstart = fbstart(file);
+	bend = fbend(file);
+
+	unionfs_lock_dentry(dentry);
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		lower_file = unionfs_lower_file_idx(file, bindex);
+
+		if (lower_file) {
+			fput(lower_file);
+			branchput(sb, bindex);
+		}
+
+		/* if there are no more refs to the dentry, dput it */
+		if (d_deleted(dentry)) {
+			dput(unionfs_lower_dentry_idx(dentry, bindex));
+			unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+		}
+	}
+	unionfs_unlock_dentry(dentry);
+
+	kfree(fileinfo->lower_files);
+	kfree(fileinfo->saved_branch_ids);
+
+	if (fileinfo->rdstate) {
+		fileinfo->rdstate->access = jiffies;
+		spin_lock(&inodeinfo->rdlock);
+		inodeinfo->rdcount++;
+		list_add_tail(&fileinfo->rdstate->cache,
+			      &inodeinfo->readdircache);
+		mark_inode_dirty(inode);
+		spin_unlock(&inodeinfo->rdlock);
+		fileinfo->rdstate = NULL;
+	}
+	kfree(fileinfo);
+
+out:
+	unionfs_read_unlock(sb);
+	return err;
+}
+
+/* pass the ioctl to the lower fs */
+static long do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct file *lower_file;
+	int err;
+
+	lower_file = unionfs_lower_file(file);
+
+	err = -ENOTTY;
+	if (!lower_file || !lower_file->f_op)
+		goto out;
+	if (lower_file->f_op->unlocked_ioctl) {
+		err = lower_file->f_op->unlocked_ioctl(lower_file, cmd, arg);
+	} else if (lower_file->f_op->ioctl) {
+		lock_kernel();
+		err = lower_file->f_op->ioctl(
+			lower_file->f_path.dentry->d_inode,
+			lower_file, cmd, arg);
+		unlock_kernel();
+	}
+
+out:
+	return err;
+}
+
+/*
+ * return to user-space the branch indices containing the file in question
+ *
+ * We use fd_set and therefore we are limited to the number of the branches
+ * to FD_SETSIZE, which is currently 1024 - plenty for most people
+ */
+static int unionfs_ioctl_queryfile(struct file *file, unsigned int cmd,
+				   unsigned long arg)
+{
+	int err = 0;
+	fd_set branchlist;
+	int bstart = 0, bend = 0, bindex = 0;
+	int orig_bstart, orig_bend;
+	struct dentry *dentry, *lower_dentry;
+	struct vfsmount *mnt;
+
+	dentry = file->f_path.dentry;
+	unionfs_lock_dentry(dentry);
+	orig_bstart = dbstart(dentry);
+	orig_bend = dbend(dentry);
+	err = unionfs_partial_lookup(dentry);
+	if (err)
+		goto out;
+	bstart = dbstart(dentry);
+	bend = dbend(dentry);
+
+	FD_ZERO(&branchlist);
+
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		lower_dentry = unionfs_lower_dentry_idx(dentry, bindex);
+		if (!lower_dentry)
+			continue;
+		if (likely(lower_dentry->d_inode))
+			FD_SET(bindex, &branchlist);
+		/* purge any lower objects after partial_lookup */
+		if (bindex < orig_bstart || bindex > orig_bend) {
+			dput(lower_dentry);
+			unionfs_set_lower_dentry_idx(dentry, bindex, NULL);
+			iput(unionfs_lower_inode_idx(dentry->d_inode, bindex));
+			unionfs_set_lower_inode_idx(dentry->d_inode, bindex,
+						    NULL);
+			mnt = unionfs_lower_mnt_idx(dentry, bindex);
+			if (!mnt)
+				continue;
+			unionfs_mntput(dentry, bindex);
+			unionfs_set_lower_mnt_idx(dentry, bindex, NULL);
+		}
+	}
+	/* restore original dentry's offsets */
+	set_dbstart(dentry, orig_bstart);
+	set_dbend(dentry, orig_bend);
+	ibstart(dentry->d_inode) = orig_bstart;
+	ibend(dentry->d_inode) = orig_bend;
+
+	err = copy_to_user((void __user *)arg, &branchlist, sizeof(fd_set));
+	if (unlikely(err))
+		err = -EFAULT;
+
+out:
+	unionfs_unlock_dentry(dentry);
+	return err < 0 ? err : bend;
+}
+
+long unionfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	long err;
+
+	unionfs_read_lock(file->f_path.dentry->d_sb);
+
+	err = unionfs_file_revalidate(file, true);
+	if (unlikely(err))
+		goto out;
+
+	/* check if asked for local commands */
+	switch (cmd) {
+	case UNIONFS_IOCTL_INCGEN:
+		/* Increment the superblock generation count */
+		pr_info("unionfs: incgen ioctl deprecated; "
+			"use \"-o remount,incgen\"\n");
+		err = -ENOSYS;
+		break;
+
+	case UNIONFS_IOCTL_QUERYFILE:
+		/* Return list of branches containing the given file */
+		err = unionfs_ioctl_queryfile(file, cmd, arg);
+		break;
+
+	default:
+		/* pass the ioctl down */
+		err = do_ioctl(file, cmd, arg);
+		break;
+	}
+
+out:
+	unionfs_check_file(file);
+	unionfs_read_unlock(file->f_path.dentry->d_sb);
+	return err;
+}
+
+int unionfs_flush(struct file *file, fl_owner_t id)
+{
+	int err = 0;
+	struct file *lower_file = NULL;
+	struct dentry *dentry = file->f_path.dentry;
+	int bindex, bstart, bend;
+
+	unionfs_read_lock(dentry->d_sb);
+
+	err = unionfs_file_revalidate(file, true);
+	if (unlikely(err))
+		goto out;
+	unionfs_check_file(file);
+
+	bstart = fbstart(file);
+	bend = fbend(file);
+	for (bindex = bstart; bindex <= bend; bindex++) {
+		lower_file = unionfs_lower_file_idx(file, bindex);
+
+		if (lower_file && lower_file->f_op &&
+		    lower_file->f_op->flush) {
+			err = lower_file->f_op->flush(lower_file, id);
+			if (err)
+				goto out;
+		}
+
+	}
+
+	/* on success, update our times */
+	unionfs_copy_attr_times(dentry->d_inode);
+	/* parent time could have changed too (async) */
+	unionfs_copy_attr_times(dentry->d_parent->d_inode);
+
+out:
+	unionfs_check_file(file);
+	unionfs_read_unlock(dentry->d_sb);
+	return err;
+}
-- 
1.5.2.2

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